Communication Product Updates

Below are brief descriptions of communications products recently developed by the Federal Highway Administration's (FHWA) Office of Research, Development, and Technology. All of the reports are or will soon be available from the National Technical Information Service (NTIS). In some cases, limited copies of the communications products are available from FHWA's Research and Technology (R&T) Product Distribution Center.

When ordering from NTIS, include the NTIS publication number (PB number) and the publication title. You also may visit the NTIS Web site at www.ntis.gov to order publications online. Call NTIS for current prices. For customers outside the United States, Canada, and Mexico, the cost is usually double the listed price. Address requests to:

When a bridge crossing a waterway is partially or entirely submerged during a flood event, its deck could be subjected to significant hydrodynamic loading. Accounting for the hydrodynamic forces that might be exerted on an inundated bridge deck is critical in the design of bridges. Specifically, the drag and lift forces, the moments acting on the bridge deck (unevenly distributed forces that can cause the bridge to overturn) under various levels of inundation, and a range of flow conditions influence the design and construction of bridges.

This report documents reduced-scale experiments and computer modeling that explore the forces acting on bridges. Analysts used three bridge deck prototypes for the experiments: a typical six-girder highway bridge deck, a three-girder deck, and a streamlined deck designed to better withstand hydraulic forces. The researchers measured the forces on each bridge deck shape in the laboratory with an ultraprecise force balance under a range of scenarios.

Analysts performed computational fluid dynamics (CFD) simulation modeling using two commercial software packages. They tested a range of model options from two-dimensional to three-dimensional. The analysts generated design equations for each of the bridge types and force coefficients.

According to the report, the CFD simulations seem promising as a method to test bridge designs, but more research is needed before complex designs can be tested wholly in the CFD realm. However, the design charts from the experimental results should be a valuable tool for bridge designers in a wide range of design applications.

For decades, transportation agencies have recognized that deterioration of concrete bridges due to corrosion of reinforcing steel is a major technical and economic challenge. As one means of addressing the problem, researchers with the Florida Department of Transportation and Florida Atlantic University are looking at corrosion-resistant reinforcements, such as stainless steels.

In the first interim report for this project, the researchers presented results from short-term tests and preliminary results from long-term exposure of reinforced concrete slabs. This, the second interim report, provides longer term data and analyses of chloride exposures that involved four types of reinforced concrete specimens, two of which simulate northern bridge decks exposed to deicing salts, while the remaining two simulate marine substructure elements.

Researchers used three concrete mix designs. Specimen types included combinations with a simulated concrete crack, bent top bar, corrosion-resistant upper bars and black steel lower bars, and intentional clad defects such as an exposed carbon steel substrate. The exposure lasted more than 4 years. The researchers ranked the candidate alloys according to performance and analyzed how they might perform in actual concrete structures.

In April 2008, FHWA's Office of Infrastructure Research and Development launched the Long-Term Bridge Performance (LTBP) program, a flagship research project with the objective of collecting scientific-quality data on the Nation's highway bridges. FHWA envisions the LTBP as a 20-year or longer examination of highway bridges to improve knowledge of bridge performance and ultimately promote the safety, mobility, longevity, and reliability of the country's highway transportation assets. This brochure details the program's objectives and methodologies.

The LTBP program aims to compile a comprehensive database of quantitative information from a representative sample of bridges nationwide, looking at critical bridge elements and the factors that affect their performance—age, material, design, condition, use, and environment. By taking a holistic approach and analyzing the physical and functional variables that affect bridge performance, the program will provide a more detailed and timely picture of bridge health and better tools for bridge management.

Printed copies of the brochure are available from FHWA's Office of Infrastructure Research and Development by phone at 202-493-3024, fax at 202-493-3442, or e-mail Monique Smith at monique.smith@dot.gov.